1. Field Of The Invention
The invention relates to an apparatus and method for the containment and control of wellhead blowouts, and particularly to the control and extinguishment of oil wellhead fires.
2. Description Of Related Art
Experts in the field of controlling wild wellheads and fighting oil well fires have long accepted a single standard method for combatting the enormous forces and dangers these wild wells and fires present. First, well in advance of fire fighters approaching the wellhead and fire area, large volumes of water are pumped into the fire area from a "safe" distance to cool the area for the fire fighters as they work. This man-made rain is continued throughout all subsequent operations. Then, a tractor-mounted crane assembly is used to remove destroyed equipment, debris, and everything that might possibly retain heat above the flash point of raining oil from the fire site. Once this is done, large amounts of explosives are brought in and detonated on or above the base of the fire to consume or interrupt the supply of oxygen, thereby extinguishing the fire. New control valves, piping and other desired equipment are fitted onto wells that can be salvaged, i.e., their preexisting production string and related equipment is not so severely damaged that it cannot control the continuing flow of oil. Irreparably damaged wells are permanently capped. In cases where an explosion has destroyed the production pipe and surrounding equipment near the ground surface, a parallel "relief"`well is drilled and the flow of oil is diverted in order to starve the wellhead of its source of crude oil. For a recent description of this standard procedure, see Sayers, "Capping Blowouts from Iran's Eight Year War," World Oil, 212:44-48 (May 1991) and the New York Times, page D1, on Feb. 28, 1991.
In a modification of this procedure, a tapered nozzle called a "stinger" is forced into the oil pipe. Pieces of rubber and rope are injected through the nozzle. These materials are picked up by the exiting oil and wedged between the nozzle and the wall of the production pipe to form a seal. When the seal is good enough so that leaks are not excessive, a thick mud slurry that is heavier than the oil is pumped into the production string to close down the oil flow. Subsequent work must be done at the well site by hand under extremely adverse conditions of heat and other factors.
An experimental device for extinguishing wellhead fires was also reported recently in the New York Times. The device was described as not requiring large amounts of water, as is required by the above-described approach. The device consists of a large tube at the end of a boom mounted on a bulldozer having a sheet metal cabin to shield the operator from the heat. The tube is to be jammed over the blazing oil pipe, funneling the fire, and either inert nitrogen gas or water is then to be pumped in to separate the flame from the oil fueling it and to cut off the supply of oxygen.
Other approaches, as reported in the New York Times of Apr. 9, 1991, include robots that launch flame-eating chemicals portable factories that spew supercold foams, air guns that cut through wreckage around wells, explosive charges that seal oil pipes, and 100-ton concrete caps that fit over the wheelhead to snuff out flames hundreds of feet high and drain away the gushing oil through pipes. It is reported that the last two simultaneously stop the uncontrolled gushing of oil.
As such, presently known methods (1) are generally quite destructive, (2) are generally very slow, (3) require large teams of workers, (4) require large amounts of water, (5) are extremely dangerous to the work teams, (6) create uncomfortable working conditions, and (7) are restrictive in the types of tools that can be used because of the risk of spark-induced reignition or explosion.